Removal of naphthenic acids from petroleum oils and fractions thereof



United States Patent REMOVAL OF NAPHTHENIC ACIDS FROMiPE- TROLEUM OILS AND FRACTIONS THEREOF George W. Ayers, Chicago, and William A. Krewer,

Arlington Heights, 111., assignors to The. Pure Oil Company, Chicago, 111., a corporation of Ohio This invention relates to a method of removing and recovering acidic oxygenated compounds from hydrocarbon mixtures containing same and, more particularly, to a process whereby hydrocarbon oils are treated with strongly-basic ionexchange resins. to produce products having low acid neutralization numbers. More specifically, the invention relates to the discovery that the presence of certain polar solvents increases the efliciency of Strongly basic ion-exchange resins to combine with highmolecular-weight, acidic, oxygenated materials, particularly naphthenic acids in lubricating oils.

It is known that acidic oxygenated materials, such as naphthenic acids, can be neutralized and extracted from petroleum stocks by a variety of solvents. One such process is described in United States Patent 2,808, 31, by

i W. L. Fierce. It is also known that crude naphthenic acids can be contacted with an adsorbent material, such as Weakly basic ion-exchange resins, for the purpose of adsorbing a portion of the naphthenic acids thereon an subsequently desorbing the resin to produce desirable fractions of petroleum naphthenic acids. United States Patent 2,723,289 by I. W. Mills is an example of such a process.

In accordance with the present invention, it has been found that the percolation of petroleum fractions containing naphthenic acids through strongly basic exchange resins results in the removal of only a very small amount of the naphthenic acids presentTT-The oil fractions so treated do not have a low enough neutralization number to make the process practical, especially from a commercial point of view. Also, the percolation of naphtha solutions of petroleum fractions, particularly heavy lubricating oil fractions such as lubricating oil extracts, through a strongly basic exchange resin is very ineffi- -cient and impractical. The application of weakly basic exchange resins in either of the foregoing processes is equally unsuccessful. In accordance with this invention, it has been found that if the percolation or other contacting of the petroleum fraction containing the naphthenic acids with a strongly basic exchange resin is carried out in the presence of a particular class of solvents, there results the removal of a large proportion of the naphthenic acids, and the resulting hydrocarbon material has .a uniquely low neutralization number, or acid content. More particularly, the solvent used in accordance with this,,invention is selected from the group consisting of methyl ethyl ketone, diethyl ketone, toluene, the xylenes, ethyl benzene, acetone, dipropyl ketone, and methyl isobutyl ketone? In general, those solvents which are used in the dewaxing art and which are polar isolvents appearto function to augment the naphthenic-acidremoving power of the resin.

Accordingly, it 'becomes a primary object of this invention to provide a process for the removal of oxygenated acidic materials from hydrocarbon mixtures containing same by treatment with a strongly basic ion-exchangeresih in, the presence of a devvaxing solvent or one or more, components of a dewaxing solvent,

Another object of the inventlon is to provide a process for removing naphthenic acids from petroleum fractions contain ng same by treatment with a strongly basic ionexchange resin inthe presence of a dewaxing solvent or one or more components of a dewaxi g solvent.

still a further objec o h n en i rela e o a p ce for emovi g naph he i cids. f m heavy lubricating oil fractions while the heavy lubricating oil fractions are dissolved in a dewaxing solvent to produce fractions which have a low acid number.

Still another object of the invention is to provide a process of producing lubricating oil fractions and/or lubricating oil solvent extracts which have low acid neutralization numbers.

These and further objects of the invention will become obvious as the description thereof proceeds.

In general, the process of this invention involves dissolving the. hydrocarbon oil fraction at least about 10% by volume of a dewaxing solvent, or one or more 7 components of a dewaxi g solvent, and treating the solution with a strongly basic ion-exchange resin, at temperatures within the range of minus 40 F. to plus 200 F. and at subatmospheric atmospheric or superatmospheric pressure, provided that the solvent does not freeze or boil under the conditions used. The resulting solution of hydrocarbon and solvent, devoid of naphthenic acids, is characterized by a low neutralization number and the hydrocarbon oil fraction may be separated from the solvent by distillation or other means. The strongly basic l resin is used until its efliciency has decreased appreciably thelr'ejatter it may be regenerated by washing with dilute caustic solution which dissolves the oxygenated acidic materials from the resin. Treatment of the resin with a low-boiling alcohol after the alkali wash is also advantageous in that it removes any deposits of sodium naphthehate which may have separated from the alkali solution due to salting-out by excess alkali. Following this, the resin is washed thoroughly with water and with the dewaxing solution, or component thereof, to complete the regeneration. It has been found that by thus regenerating strongly basic ion-exchange resins, the regenerated resin has approximately the same ability to remove naphthenic acids from petroleum fractions asdoes fresh resin. The resins used herein may be regenerated many times and do not appear to lose their aflinity for naphthenic acids under the conditions of the instant process.

Although this process is designed to remove acidic oxygenated materials from hydrocarbon mixtures containing same,-it is particularly applicable to the removal of naphthenic acids from lubricating oils and fractions, including solvent extracts from the manufacture of both neutral oils and bright stocks. The naphthenic acids found in lubricatihg oil and fractions thereof are generally character- .ized as high-molecular-weight carboxylic acids, liquid or taining from 25% to oil. The market value of these acids is increased many-fold by purifying the acids through removal of the remaining oil. The instant process may be used for the purpose of removing small 'cordance with the instant process.

amounts of naphthenic acids from hydrocarbon oils containing same, or for the purification of solutions of naphthenic acid in oil that have been obtained from various oil purification processes.

pane and cresylic acid. Since solvent extraction and the solvent extracts produced thereby are well known, there is no necessity for further description for purposes of this invention. It sufiices to -say that one skilled in the Various types of hydrocarbon oil mixtures containing art may have reference to one or more of the United acidic oxygenated materials, including naphthenic acids, States patents which describe in greater detail the solvent may be treated in accordance with this invention. Any extraction process and give the characteristics of solvent hydrocarbon oil fraction which can be improved by a extracts that may be benefited by the process of this treatment which lowers the acid neutralization number invention. is included as a material susceptible to treatment. Lubri- The following table gives the physical and chemical cating oil fractions, particularly neutral oils, bright stocks, properties of several solvent extracts and lubricating oil. and solvent extracts from the manufacture of neutral oils fractions which are illustrative of the types of material and bright stocks, can be advantageously treated in acthat may be treated in accordance with this invention.

TABLE I Characteristics of oils and extracts that may be beneficiated by the process of this invention A. PHENOL EXTRACTS Name Sample API Flash Fire Vis. 100 Vis. Vis. NPA Pour, Percent Percent V.I.

No. Gravity F. 130 F. 210 F Color F. Sulfur .R.

High V.I. Br. StOck 1- 20 26. 9 590 650 2, 450 938 155. 5 +6 0. 71 100 High V1. 140 Br Stock" 21 26. 6 570 630 2.180 838 141.4 +5 0.68 98 High V.I. 200 Neut 22 30. 6 425 485 193. 6 102 46.1 1 0. 02 99 Mid-Cont. NeutraL 23 29. 8 425 480 185. 5 98. 9 45. 5 0. 29 98 Mid-Cont. Neutral. 24 31.0 425 174. 2 44. 8 0. 0 100 Sinclair 120 Br. Stock 25 25. 2 540 600 1,993 749 125.7 0.62 90 Sinclair 200 Neut 26 29.7 410 470 201 105 46 0.01 91 Mid-Cont. 500 Neut- 27 28. 3 475 535 527 232 63. 1 0. 06 89 Mid-Cont. 120 Br Stk 28 27.0 525 595 1,731 668 121. 6 0.58 96 MldCOnt. 150 Br. Stk 29 27. 5 2, 420 148. 9 86 C. NON SOLVENT REFINED Penn. 150 Neutral 30 155 43.0 87 Gulf Coast Br. Stk 31 16. 9 505 560 601.0 1, 537 147. 5 Iii-3% +20 0. 395 0. 83 10 Raw Neut. (dewaxed) 32 22. 4 435 500 356 159 51. 4 7+ 0 1. 23 0. 1 Mid-Cont. 200 Neut- 33 26. 3 400 455 206. 6 104 45. 5 +2% +15 0. 46 0. 05 76 benzene, mixtures of sulfur dioxide and nitrobenzene;

mixtures of phenol and water, and the well-known Duosol solvent. This latter solvent comprises a mixture of pro- It has been found that strongly basic ion-exchange resins of the polystyrene quaternary ammonium type and the styrene-divinylbenzene copolymer quaternary ammonium type exhibit properties which make them particularly efiicient for the purposes of this invention. EX- amples of these resins include Amberlite IRA-400, Amberlite IRA-401, Dowex 1 and Dowex 2. The Amberlites are manufactured by the Rohm & Haas Company and the Dowex resins are produced by the Dow Chemical Company. These materials are described throughout the literature, including Kunins text on Ion Exchange Resins," second edition (1958), Osborns text on Synthetic Ion Exchangers (1956)" and the Dow Chemical Companys brochure entitled, Dowex Fine Mesh Resins.

These strongly basic exchange resins are available in the chloride. salt form which. may be converted into, the active hydroxide form by treatment with sodium .hyvdroxide solution just before: use. The active :hydrox'ide form contains strongly .basic'quatemary 'ammonium'hy droxide groups on the resin surface. When :an oil or oil mixture containing naphthenic acids is contacted with amass of. such active :resin particles, the naphthenicqacids appear to react chemically with. the quaternary. ammonium hydroxide group in accordance with. the iollowing illustrative equation,

The resulting quaternary ammonium naphthenate salt remains on the resin surface because the naphthenate ions are held chemically by the quaternary ammonium ions forming the resin surface. In contradistinction to the foregoing action of strongly basic ion-exchange resins,

particularly in the presence of polar liquids, the weakly basic ion-exchange resins contain amine groups which show a much diminished tendency to combine with naphthenicacids. Consequently, in the presence of polar solvents a large portion of the naphthenic acids remains in solution in the oil-solvent mixture, and hence is not removed by the resin. Moreover, most petroleum fractions contain trace amounts of water which hydrolyzes naphthenates of the amines, but not the quaternary ammonium naphthenates. The resin itself also usually contains a considerable amount of water, which also results in diminished naphthenic acid removal by the weakly basic resins. Traces or small quantities of water are of no importance in the removal of nap'hthenic acids from petroleum fractions by strongly basic ion-exchange resins of the quaternary ammonium type unless the water is present in suflicient amount to prevent contact of the oil solution with the resin surface. Accordingly, when solutions of oils dissolved in polarsolvents,such as benzene,

toluene or acetone, are percolated through weakly basic ion-exchange resins, essentially all of the high-boiling naphthenic acids pass through with the oil and polar solvent without appreciable adsorption on the resin sur- Even the use of a non-polar solvent, such as- .face. aliphatic naphtha, which is used to lower the viscosity and hence increase the contacting eificiency, does not sufliciently improve the affinity of weakly basic ion-exchange resins for naphthenic acids to make their use practical.

In order to illustrate the invention, the following nonlimiting examples are given:

Example 1.A 100 cc. burette provided with a glass stopcock was fitted in the following manner to serve as a percolation vessel: A small wad of glass wool was placed in the bottom'of the burette, after which the burette was half-filled with solvent composed of 55 vol. percent toluene and 45 vol. percent methyl ethyl ketone. A strongly basic ion-exchange resin (Amberlite IRA- 400), Which'hadbeentreated on a Buchner funnel with .six volumesof 4% sodium hydroxide solution and washed with water until the effluent had a pH of 7 .0, was added '6 slowly: .to. theburette while the burette was in contact with a mechanical "vibrator. The addition was stopped when the burette contained cc. of the resin. The top of the burette was then attached to a reservoir by means 'of-a-rubber stopper.

A mixture of 1555 cc. of solvent (55 vol. percent toluene-.45 vol. percent methyl ethyl ketone) and 545 cc. of lubricating oil extract (acid neutralization number=3.5'4-) was poured into .thereservoir and percolated through the column of resin at a rate of approximately 1 to .-1.5 cc. per minute. The percolate'was collected in fractions which were then stripped of solvent by distillation and the oil analyzed for acid content (acid neutralizalrjtiion number). The results are shownin the following ta ez,

TABLE .11

Yield orstrip edf Oil (ce.) intFrac-Z tion Fraction No.

' Example 2.-An experiment carried out similarly to Example .1 except that the solvent was straight V;Ml & P. naphtha. Data on this percolation areas :follows:

TABLE III Yield of Stripped Acid Neutralira- Fractlon No. Oil (00.) in Fraction Number 01 tion Stripped Oil Fraction Original ml 3, 54

Example 3.An experiment was carried out similarly to Example 1 except that the solvent was straight methyl ethyl ketone. Data on the percolation are as follows:

TABLE IV Yield of Stripped Acid Neutraliza- Fraction No. Oil (00.) in Fraction Number of tion Stripped Oil Fraction Original oil 3. 54 1 19 0.13

Examplet- An experiment was carried outsimflarly to Example 1 except that the solvent was straight toluene. Data on thepercolation are as follows:

ization numbers of the stripped oil fractions were in close agreement with those obtained with fresh resin.

In order to illustrate the effectiveness of Amberlite TABLE V IRA-401 (a strongly basic ion-exchange resin) over Am- 5 berlite IR-4B (a weakly basic ion-exchange resin), a

Fraction No giei tggs t ri pgg series of experiments was conducted in which l-cc. t'ion stripped on portlons of an ml solution containing 18.5 vol. percent Fraction of dewaxed bright stock (Acid Neutralization Number=0.21), 36.5% methyl ethyl ketone and 45.0% toluilriginaln" 5-83 '10 one were shaken in a batchwise operation with cc. of 11 the respective exchange resins. The Amberlite IRA-401 i- 8-8? was activated as in Example 1 with 4% sodium hydroxide 1 solution to convert the chloride form of the resin into g-g the active quaternary ammonium hydroxide form before 1 "(iii use in the series of runs. Bright stock contains highboiling naphthenic acids which are far more diflicult to 12.5 0.06 20.0 remove by ordlnary means than the naphthenic ac1ds cong-g tained in neutral oils. Washing with ordinary caustic 1110 "(iii soda solution is completely ineifective for the removal of g-g 20 the naphthenic acids from bright stock. The results of 1630 0:81 the series of experiments are shown in Tabe VI: 3813 "613B TABLE VI Evaluation of anionic exchange resins (batch-treating Example 5 .-A column of strongly basic ion-exchange method) resin (Amberlite IRA-400), prepared according to direcon solution used: tions given in Example 1, was used for th removal of 18.5% 150-100 dewaxed bright stock (Acid Neut. No. 0.21). naphthenic acids from an extract dissolved in a mixture 22137 g g ggf of toluene and methylethyl ketone until the resin had become spent and no longer removed appreciable quan- Add New. oalwlated' tities of naphthenic acids from the extract. The spent Rlm c a ge Resin St Negi Pefi'ceutAgld resin was washed with fresh solvent mixture to remove rpm I move the entrained extract, then it was washed with 6-7 volumes of 2% sodium hydroxide solution to remove the fifigfiiii gait: 8 82 i3 naphthenic acids held by the resin. After the resin had Amberlite IR-4B 5 been washed further with approximately 2 volumes of methanol it was washed with water until the efiluent water had a pH of approximately 7.0. The resin was The effective life of the strongly basic ion-exchange resins without regeneration is shown in Table VII:

TABLE VII Percolation of dewaxed bright stock and neutral oil solutions through basic exchange resins Solvent Used: Mixture of vol. percent toluene and 45 vol. percent methyl ethyl ketone. Amount of Resin Used: cc. (61 g.).

Total Wgt. Bbls. oi Avg. Acid Ratio oi of Oil Oil N eut. No. Run No. Exchange Resin Solvent Temp., Rate, Passed treated of total oil to oil F. ccJmin. Exclusive per Cu. passed of Solvents Ft. of through (g.) Resin Resin (A) Runs with Vis. dewaxed bright stock (0.21 Acid Neut. No.)

Amberlite IRA-401 l 11. 5 77 0. 5 1,015 2. 0 0. 07 Amberlite IRA-401 4. 4 77 0. 5 1, 456+ 2. 9+ 0. 05 Amberiite IRA-401 4. 4 150 0. 5 l, 536 3. 1 0. 05 Amberlite IRA-400 4. 4 77 0. 5 65 0. 1 0.18 Amberlite IRA-400 11. 5 77 0. 5 0. 4 0. ll Amberlite IRA-400 11. 5 150 O. 5 251 0. 5 0.11 Amberlite IRA-400 4. 4 77 0. 5 32 6 0. 17

(B) Runs with 220 Vls. dewaxed neutral (0.17 Acid Neut. No.)

Amberlite IRA-400 4. 0 77 1.0 507 1. 0 0. 04 Amberlite IRA-400 4. 0 77 1.0 564 1. 1 0.05 Amberlite IRA-400 L 4.0 77 1. 0 455+ 0.9+ 0. 04

1 Activated resin contained 25% water as shown by refluxing with toluene.

1 Activated resin contained 16% water as shown by refluxing with toluene.

3 Activated resin was heated at 220 F. for 72 hours (38% loss in weight) before use. 4 Regenerated resin.

then washed with acetone and used for the removal of Another aspect of this invention is the application of naphthenic acids from lubricating oil extract according to the directions given under Example 1. After removal the resin-treating step to a lubricating oil fraction during the process of refining while same is still in solution in of solvent from the percolate fractions, the acid neutral- 75 the dewaxing solvent.

It -,is;custemary;in the industry to manufacture lubricatring Oils, or'lubricating oil fractions, by subjecting :the oil successively :to solvent F6XtIZlCtlO11, SO1V6I1t dewaxing and .clayqcqntacting. These processing steps are regulated so ithatzthe finished oil has an acid neutralization number not greater than 0.1 and preferably as low a value as possible. ESince petroleum oils from ditferent sources wary =Withtrespect to their content of naphthenic acids, it ziszsometimes difficult to obtain a finished oil having the desired neutralization number.

We have :found that .a :large proportion of the naphtthenic .acids are readily removed from glubricatingoils r-when .the :latterare in solution in-dewaxing-solvent and the solution .is percolatedthrough, .or;contacted with, :a

strongly basic ion-exchange resin. (This means that .the

as Amberlite'IRA-401, :to remove ,ailarge proportion of ,the ,naphthenic acids before the dewaxing solvent :is ,dis-

,rtilled from the oil. The so-treated, solvent-Lfree oil is then treated with clay in a conventional manner to obtain a tfiuished'lubricating oil or fraction whichhas a very low or .negligibleracid .number. The addition .of this extra processing step between dewaxing and clay-treating thus nnakespossible the production of finished lubricating oil fractions having very low acid-neutralization numbers, a result which, if obtainable .at all with lubricating :oils from certain crude oil sources, could be effected-other- -wise only with great difiiculty and expense.

Since it is known that solutions of lubricating :oils in o,r'ciinary naphthas such as 'VM -& P naphtha and Stod- .dard Solvent are not effective 'for efiicient "removal of naphthenic acids from the oil by basic ion-exchangeresins, {it was surprisingto find-thatdewaxing solvent,-which .norrnally .consists'of a mixtureo'f aromatic hydrocarbons and ketones, was a very great aid in the removal of naphlthenicacids from the oils by strongly basic ion-exchange iTeSinS.

The effectiveness of a dewaxing solvent, composed of 55 volume percent toluene and 45 volume percent methyl ethylketone, in the removal of naphthenic acids from a dewaxed neutral by a strongly basic exchange resin (Amberlite IRA-400) is shown in Example 6. The use of VM & P naphtha instead of dewaxing solvent results in very little naphthenic acid removal from the lubricating oil "by the .strongly basic ion-exchange resin.

Example 6.A 100-00. burette provided with a glass stopcock was fitted in the following manner to serve as a percolation vessel. A small wad of glass wool was placed in the bottom of the burette, after which the burette -.was half-filled with solvent composed of 55 voltmnepercent toluene and 45 volume percentmethyl ethyl .ketone. A strongly basic ion-exchange resin (Amberlite IRA-400), which had been treated on a Buchner funnel with six volumes of 4% sodium hydroxide solutionand washed with water until the effluent had a pH of 7.0, was added slowly to-the burette which was in contact with a mechanical vibrator. The. addition was stopped when the burette contained 100 cc. of the resin. The top of the burette was then attached to a reservoir by means of a rubber stopper.

A mixture composed of volume percentof dewaxed neutral oil, having a S.U.S. viscosity of 200 at 100 F. and :an acid neutralization number of 0.17, and 80 volume percent of dewaxing solvent of the composition mentioned above was poured into the reservoir and percolated through the column of resin at the rate of 1 to 1.5 cc. per minute. The percolate was collected in fractions .which were then stripped of solvent by distillation and the oil analyzed for acid content (expressed as acid neu- "TABLE VIII Yield of'stripped Acid neutralizaoil (cc.)':in frac-. tiorrnumber of .tion gstrlppidoiltracion Fraction No.

pn inai nil The dewaxingesolvents suitable .for the purposes of this aspectoftheinvention are'those-materials used ordinarily :in the dewaxing operation; therefore, no special solvent .removal of the wax by filtration is treated with the strong- .ly basic-ion-exchange resin either by percolation or other contacting at the prevalent temperature, after which the :dewaxing-solvent is removed from the oil in the usual :manner.

The particular dewaxing solvent composition .and 'thezconditions, such as temperature, are dictated by -the;requirements of the solvent dewaxing-operation.

In the percolation method of operation, the hydrocar- -bon oil solutionis passed through a bed .of .resin,granules ,untilthe acid neutralization number of the stripped oil reaches a specified value; then the hydrocarbon .oil solution stream is switched to a fresh bed of resin granules while the first bed is subjected to regeneration. In the contact method .of operation, the hydrocarbon oil solution is contacted with a definite proportion of the activated resin, after which the hydrocarbon oil solution issseparated by conventional means from the resin. In general, .a sufiicient amount of the strongly basic resin is used to accomplish complete neutralization of the acidic oxygenated compounds present in the hydrocarbon mixture being treated. Preferably, a slight excess over stoichiometric'amounts of the resin, basedon its ,basicity, are .used. Usually, it is only necessary to contact each barrel of hydrocarbon mixture with about 0.3 to 2 cu. .ft. of resin although smaller amounts may be used when the quantity of acidic oxygenated compoundspresentis small. .As the content of acidic oxygenated compounds in the hydrocarbon mixture to be treated increases, the amount of resin used per unit volume-or unit weight .of hydrocarbon mixture must be increased. On-the. average,.about one cubic foot of resin will satisfactorily treat two barrels of heavy oil.

The amount of non-aliphatic dewaxing solvent, or com- ;ponent thereoflused may vary with the physical properties of the hydrocarbon mixture and the ratios of hydrocarbon mixture to resin used. The solvent should be:pr.esent in an amount sutficient to thoroughly saturate resin. .In general, about 10 to volume percent based on the volume of hydrocarbon mixture and solvent solution .is sufiicient. One functionof the solvent .is to reduce .the viscosity of the hydrocarbon mixture so asto obtainrintimate contact with the resin. .Another function, in accordance with this invention, is to increase-the ,selectivityand efliciency of the neutralization 11 The process may be carried out batchwise or continuously, and by percolation or other contact methods. Any known technique for bringing together a solid and a liquid in intimate contact may be employed. The temperatures of the contacting may be ambient to as high as 200 F.,

the resin as a bed through which the hydrocarbon mixture is percolated may be used. One technique that is applicable comprises intimately mixing a given volume of the hydrocarbon mixture with a granular massiof the resin and separating the liquid phase of decantation, filtration or centrifugation. Other known methods of separation may be used. The process may be made continuous by employing a column or contact chamber adapted to remove the spent or partially spent resin and adding fresh resin as needed. The efficiency of the removal of acids can be carefully followed by the neutralizationnumber of the product. Various diluents may be used to recover any hydrocarbon mixture retained in the resin bed. Preferably, the retained hydrocarbon mixture is washed out with small portions of a non-aliphatic dewaxing solvent.

The solvent may be introduced as a mixture with the hydrocarbon to be treated, or the solvent and hydrocarbon mixture may pass in layers or intermittently through the bed of resin. It is only essential that the solvents herein-specified be present at the time of contact of the resin with the hydrocarbon mixture. Other modifications of this aspect of the invention will become apparent to one skilled in this art.

Examples of suitable resins are strongly basic anionic exchange materials such as Rohm and Haas Amberlite IRA-401, Amberlite IRA-400 and Amberlite IRA-410 and Dow Chemical Companys Dowex 1 and Dowex 2 (or Nalcite SAR). Such weakly basic anionic exchange resins as Rohm and Haas Amberlite IR-4B and Amberlite IR-45 and Dow Chemical Companys Dowex 3 and Chemical Process Companys Duolite A-114, Duolite A-4 and Duolite A-7 are ineffective for use in the process of this invention. Commercially, known strongly basic anionic exchange resins and weakly basic anionic exchange resins vary greatly in their basic strength, according to the publication Ion Exchange Resins, second edition, by Robert Kunin, Wiley and Sons, 1958.

The distinction between a weakly basic resin and a strongly basic resin is known in the art.

Acid removal by a strongly basic resin occurs through the formation of hydrolysis-resistant quaternary ammonium salts at the resin surface; even very weak acids such as boric acid and silicic acid are readily removed from various fluids by these resins. Weakly basic resins exert an action on acids which is closely allied to adsorption; most very weak acids cannot be removed in appreciable amount from fluids by this type ofresin.

Amberlite IRA-400 and Amberlite IRA-410, and a more porous form of Amberlite IRA-400 called XE-75, are strongly basic anion exchange resins which are described by the manufacturer as styrene copolymers chloromethylated and aminated to quaternary ammonium derivatives. Dowex 1 and Dowex 2 are strongly basic anion exchange resins of the quaternary ammonium type, which contain styrene-divinylbenzene structural units.

What is claimed is:

1. The method of removing high-molecular-weight acidic oxygenated compounds boiling above about 600 F. from mineral lubricating oils which comprises treating said mineral lubricating oils with a strongly basic anionic exchange resin in the presence of a solvent of the group consisting of aromatic hydrocarbon dewaxing solvents and keton dewaxing solvents and mixtures thereof.

2. The method in accordance with claim 1 in which the mineral lubricating oil is selected from the group of heavy mineral lubricating oils and solvent extracts produced in the refining of mineral lubricating oils.

3. The method in accordance with claim 2 in which the mineral lubricating oil is heavy mineral lubricating oil.

4. The method in accordance with claim 1 in which said strongly basic anionic exchange resin is selected from the group of polystyrene quaternary ammonium compounds and styrene-divinylbenzene copolymer quaternary ammonium compounds.

5. The method in accordance with claim 2 in which said mineral lubricating oil is a solvent extract produced in the refining of mineral lubricating oils.

6. The method in accordance with claim 3 in which the heavy mineral lubricating oil is a bright stock.

7. The method in accordance with claim 1 in which said solvent is a mixture of toluene and methyl ethyl ketone. I

8. The method in accordance with claim 1 in which said high-molecular-weight organic acids are naphthenic acids.

9. The method of treating a mineral lubricating oil containing high-molecular-weight acidic oxygenated compounds boiling above about 600 P. which comprises passing said mineral lubricating oils into contact with a strongly basic anionic exchange resin in the presence of a solvent of the group consisting of aromatic hydrocarbon dewaxing solvents and ketone dewaxing solvents and mixtures thereof, separating a solvent solution of said mineral lubricating oil, freed of a substantial amount of said acidic oxygenated compounds, from said resin, recovering said mineral lubricating oil from said solvent and recovering said acidic oxygenated compounds from said resin.

10. The method in accordance with claim 9 in which the mineral lubricating oil is selected from the group of heavy mineral lubricating oils, and solvent extracts produced in the refining of mineral lubricating oils and said acidic oxygenated compounds are high-molecular-weight naphthenic acids.

11. The method in accordance with claim 9 in which said solvent is a mixture of toluene and methyl ethyl ketone.

12. The method in accordance with claim 9 in which said strongly basic anionic exchange resin is selected from the group of polystyrene quaternary ammonium compounds and styrene-divinylbenzene copolymer quaternary ammonium compounds.

13. The method of producing mineral lubricating oils of reduced neutralization number which comprises contacting a mineral lubricating oil that has been subjected to refining, including the Step of dewaxing and dissolution in a solvent of the group consisting of aromatic hydrocarbon dewaxing solvents and ketone dewaxing solvents and mixtures thereof after the separation of wax therefrom, with a strongly basic anionic exchange resin, whereby the high-molecular-weight acidic oxygenated compounds boiling above about 600 F. therein are combined with the resin, separating said resin from said solvent mineral lubricating oil solution, and subjecting said lubricating oil to finishing treatments.

14. The method in accordance with claim 13 in which the mineral lubricating oil is a heavy mineral lubricating oil.

15. The method in accordance with claim 14 in which the heavy mineral lubricating oil is a bright stock.

16. The method in accordance with claim 13 in which said strongly basic anionic exchange resin is selected from the group of polystyrene quaternary ammonium com- 13 pounds and styrene-divinylbenzene copolymer quarternary ammonium compounds.

17. The method in accordance with claim 13 in which said solvent is a mixture of toluene and methyl ethyl ketone. 5

18. The method in accordance with claim 13 in which said acidic oxygenated compounds are high-molecularweight organic acids.

19. The method in accordance with claim 18 in which said high-molecular-weight organic acids are naphthenic m acids.

References Cited in the file of this patent UNITED STATES PATENTS Ayers et al. Mar. 17, 

1. THE METHOD OF REMOVING HIGH-MOLECULAR-WEIGHT ACIDIC OXYGENATED COMPOUNDS BOILING ABOVE ABOUT 600* F. FROM MINERAL LUBRICATING OILS WHICH COMPRISES TREATING SAID MINERAL LUBRICATING OILS WITH A STRONGLY BASIC ANIONIC EXCHANGE RESIN IN THE PRESENCE OF A SOLVENT OF THE GROUP CONSISTING OF AROMATIC HYDROCARBON DEWAXING SOLVENTS AND KETON DEWAXING SOLVENTS AND MIXTURES THEREOF. 